He said America was still "knee deep in the first wave" of the pandemic.
"If you look at the graphs from Europe – the European Union as an entity, it went up, and then it came down to baseline. Now they're having little blips, as you might expect, as they try to reopen. We went up, never came down to baseline, and now we're surging back up.
"It's a serious situation that we have to address immediately."
Today, US President Donald Trump said he disagreed with Fauci, who remains a senior member of the White House's Coronavirus Task Force.
"I think we are in a good place, I disagree with him," the President told Greta van Susteren, the host of a TV show called Full Court Press.
"We've done a good job. I think we are going to be – in two, three, four weeks, by the time we next speak, I think we are going to be in very good shape."
"Dr Fauci said don't wear masks. Now he says wear them," he added, implying Fauci's advice could not be trusted.
Last month, Fauci was asked why Americans were initially told they didn't need to wear masks. He said there were concerns, at the time, about hospitals and health workers running out of personal protective equipment.
"Even though there appears to be some contradiction of, 'You were saying this then, why are you saying this now?' actually the circumstances have changed. That is the reason why," Fauci said.
Today's record-breaking figure came as Trump pushed for schools across the US to reopen, and accused officials opposed to the idea of being motivated by politics.
"We want to reopen the schools," he said.
"We don't want people to make political statements or do it for political reasons. They think it's going to be good for them politically, so they keep schools closed. Now way."
He was backed up by Health and Human Services Secretary Alex Azar.
"Parents have to get back to the factory. They've got to get back to the job site. They have to get back to the office. And part of that is their kids, knowing their kids are taken care of," said Azar.
But a number of groups representing teachers came together to condemn the idea.
"The White House and the Centres for Disease Control and Prevention have offered at best conflicting guidance for school reopening, and today offered little additional insight," the groups said.
"Without a comprehensive plan that includes federal resources to provide for the safety of our students and educators with funding for personal protective equipment, socially distanced instruction and addressing racial inequity, we could be putting students, their families and educators in danger."
